Field of the Invention
The present invention relates to a display device, and more particularly, to a display device having two touch functions.
Discussion of the Related Art
Touch panels are a type of input device that is included in display devices, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), organic light emitting display devices, electrophoretic display (EPD) devices, etc., and enable a user to input information by directly touching a screen with a finger, a pen or the like while looking at the display device.
There are various methods where the display devices sense a touch by using a touch panel.
For example, a touch sensing unit may sense a capacitance variation of each of touch electrodes included in a touch panel when a finger contacts the touch panel, thereby determining whether or not there is a touch. Touch panels based on such a method are referred to as capacitive touch panels.
In another example, the touch sensing unit may sense a variation of a capacitance caused by a change in an interval between two touch electrodes spaced apart from each other, thereby determining whether or not there is a touch. Touch panels based on such a method are referred to as pressure touch panels.
In a related art display device including a capacitive touch panel and a pressure touch panel, the capacitive touch panel may be built into a panel that displays an image, or may be attached on the panel. The pressure touch panel includes a first pressure electrode having a plate type and a plurality of second pressure electrodes arranged in a block type. In this case, the first pressure electrode is disposed between a first substrate configuring the panel and a first polarizing film, and the second pressure electrode is disposed under a light guide plate.
In the display device including the capacitive touch panel and the pressure touch panel which are driven in different manners as described above, interference can occur between touch electrodes configuring the capacitive touch panel and the first pressure electrode. Therefore, noise can be added into a capacitance touch sensing signal generated in the capacitive touch panel, and moreover, noise can be added into a pressure touch sensing signal generated in the pressure touch panel.
Moreover, since the first pressure electrode is provided on a lower end of the first substrate including various elements for displaying an image, noise can be added into the pressure touch sensing signal generated in the pressure touch panel. Also, in this case, noise is added into signals supplied to the elements, and for this reason, an image cannot normally be displayed.
Moreover, since the first polarizing film is disposed between the first pressure electrode and the second pressure electrode, an interval between the first pressure electrode and the second pressure electrode increases, and for this reason, a sensitivity of the pressure touch sensing signal generated in the pressure touch panel can be reduced. Particularly, if the display device is an LCD device, a light guide plate or an optical sheet is disposed between the first polarizing film and the second pressure electrode, and for this reason, a sensitivity of the pressure touch sensing signal generated in the pressure touch panel can be more reduced.